136 A SYNOPSIS OF THE INDIAN TRIBES. [iNTROD. SECTION V. GENERAL OBSERVATIONS. The Rocky Mountains are the great line of demarcation, in reference both to climate and to the means of subsistence which the country in its natural state affords to its inhabitants. The difference between the climate of the Atlantic shores of North America and the opposite European coast, is well known. It consists less in that of the summer heat, which, though greater on the American than on the European side of that ocean, does not vary essentially under the same latitudes, than in the intensity of the cold in the American winters. This is such as to make a difference equivalent to one of more than ten degrees of latitude. Neither the Alleghany Mountains, nor the less elevated transversal chain which seems to extend from the river Saguenay to the sources of the Saskachawin, produce any sen- sible change in that respect. The comparative observations, made at several military posts, show on the contrary, that the excess both of heat and cold respectively is greater, in the valley of the Mississippi and the adjacent prairies, than on the shores of the Atlantic. * It may be said generally, that, with variations arising from local causes, the same climate prevails from the seacoast to the Rocky Mountains. But the country lying west of that chain, and more particularly that portion which lies along the Pacific, enjoys a climate similar to that of Western Europe. Since it is also ascertained, that the climate of Pekin is the same with that of Philadelphia, and that the temperature both in summer and winter of the eastern coast of Asia, north of the Torrid Zone, corresponds generally with that of the eastern coast of North America, under the same latitudes, it appears certain that this difference of climate arises from the respective exposure of the seacoasts. Those which face the west enjoy a much more temperate climate than those which have an eastern exposure. In order to account for such a general result, we must seek for an equally general cause. Apart from the
- This may perhaps be accounted for, by the winds, which, whether
from the south or from the north, sweep that immense valley, without being intercepted by any sufficient transversal chain of mountains.
